This invention relates to displaying information and more specifically, displaying text on a radial display.
Often times there is a need to display textual information regarding the status of an aircraft to an operator of the aircraft or service personnel. For example, when performing diagnostic tests on an aircraft, it is important to display information regarding aircraft parameters to the service personnel. Unfortunately, due to space and cost limitations, dedicated screens for diagnostic information cannot always be provided.
Therefore, the textual information needs to be displayed on existing displays. One display that is available for displaying textual information in a typical aircraft is the weather radar display. The weather radar display is normally used to display weather information detected by the weather radar. The weather radar detects rainfall by emitting an electromagnetic pulse from the weather radar antenna of the aircraft. The pulse is reflected by the water droplets of rain back to the aircraft. The weather radar interprets the reflected signal. The distance to rain is proportional to the time it takes from emitting a pulse to the time it takes to detect a return pulse. The signal strength of the signal is roughly proportional to the intensity of the rainfall.
This information is displayed on a weather radar display. Typically weather radar displays are color cathode ray tube (CRT) displays or color flat panel displays. The weather radar display typically displays the intensity of rain using a spectrum of colors from green to yellow to red to magenta, with green representing light rain and magenta the heaviest.
In a weather radar display the display is drawn as a scan line sweeps across the display, typically from left to right (in some weather radar displays the radial may sweep from right to left, may sweep from right to left and then left to right, or may open like a fan). Because of the way the weather radar display is drawn, such a display is also known as a radial or rho-theta display. In one embodiment of a weather radar display the radar image is comprised of 512 scan line position with each scan line having 512 pixels, also known as range bins.
The problem with using the weather radar display to display text is that the way the scan line moves across the screen makes it difficult to display clear, straight text. Text displayed on a weather radar is typically displayed as curved text, somewhat like text written on the curve of a rainbow. For example, U.S. Pat. No. 5,805,100 entitled xe2x80x9cMethod and Apparatus for Universal Display of Alphanumeric Data on Radar Displaysxe2x80x9d and issued on Sep. 8, 1998 to Becker et al., shows text displayed in such a manner. This limits the utility of the weather radar display for displaying textual information. In order to utilize the weather radar screen for text display what is needed is a method for displaying information on a radial display.
In one embodiment of the invention, a method for displaying text aligned in a virtual Cartesian grid on a radial display is disclosed. In a first step a range bin value on a scan line is converted from a polar coordinate value to a rectangular coordinate value. Next, a virtual text grid location corresponding to the rectangular coordinate value is located. The character assigned to the virtual text grid location is determined. Then a pixel location within the virtual text grid location based on the font matrix of the character assigned to the virtual grid location is determined. The range bin value location is then associated with an attribute of the pixel location. These steps are repeated for each range bin values along a scan line and for each scan line. The text is displayed on the radial display based on the polar coordinates of the range bin values and the associated attributes.
In another embodiment, a display system for displaying text aligned with a horizontal axis on a radial display having a plurality of pixels addressed using a polar coordinate system is disclosed. The system comprises a processor memory, the processor memory including a text array storing the text information to be displayed, the text array comprising a plurality of text records, each of the plurality of text records containing a character to display, a foreground color and a background color. A font array comprising a plurality of font matrixes, is also stored. Each font matrix represents a xe2x80x9cmxe2x80x9d by xe2x80x9cnxe2x80x9d bit mapped character that can be displayed as part of the text array. The system also includes a processor unit in communication with the processor memory. The processor unit is operable to calculate a rectangular coordinate value equivalent for each of a plurality of range bin values along each of a plurality of scan lines. Further the processor unit may determine in which text record the calculated rectangular coordinate value equivalent is located to determine a current character, a current foreground color and a current background color. Then the processor unit associates the range bin value along the scan line with a color code, the color code being either the current background color or the current foreground color. The selection of the background color or the foreground color is done by using the font matrix corresponding to the current character to determine if the pixel location corresponding to the range bin value is part of the current character (foreground color) or part of the background (background color). The color code for each range bin values and for each scan lines is sent to the radial display by the processor unit for presentation.